Minor date format code cleanup

app/src/main/java/eu/kanade/tachiyomi/util/DateExtensions.kt

@@ -0,0 +1,10 @@
+package eu.kanade.tachiyomi.util
+
+import java.text.DateFormat
+import java.util.Date
+
+fun Date.toTimestampString(dateFormatter: DateFormat): String {
+    val date = dateFormatter.format(this)
+    val time = DateFormat.getTimeInstance(DateFormat.SHORT).format(this)
+    return "$date $time"
+}